Mushroom Multiplication

Grade Level(s)

6 - 8

Estimated Time

Two or three 50-minute class periods

Purpose

Learn about edible mushroom cultivation and how one mushroom multiplies into many more! Create a spore print, and explore ecology concepts by experimenting with mold and yeast growth and researching species of fungi.

Vocabulary

fermentation: a chemical breaking down of a substance (as sugar) that is controlled by an enzyme, usually does not require oxygen, and typically results in the production of alcohol and carbon dioxide

fungi: members of the kingdom of living things (as mushrooms, molds, and rusts) that have no chlorophyll, must live in or on plants, animals, or decaying material, and were formerly considered plants

yeast: any of about 1,500 species of single-celled fungi that ferment sugar to produce alcohol and carbon dioxide

psychrophilic: organisms that are capable of growth and reproduction in very cold temperatures (-20° C to +10° C)

club fungi: of the family of fungus with a simple or club-shaped sporophore

rust: fungal disease of plants that results in reddish or brownish patches

Did you know? (Ag Facts)

For every person on earth there are approximately 2 tons of fungi.1

Experts estimate that there may be as many as 1.5 million species of fungi.1

The oldest fossil fungus found was estimated to be 545 million years old - older than the first flowering plants.1

Giant Puffball mushrooms can grow so big that they have been mistaken for sheep.1

Background - Agricultural Connections

Yeasts are small, single-celled organisms. They are members of the kingdom Fungi (singular, fungus), that also includes mushrooms and differs from plants in that these organisms have no chlorophyll. Yeasts have been useful to humans for centuries in the production of certain foods and beverages. They are responsible for the rising of bread dough and the fermentation of wine, whiskey, brandy, and beer. They also play the initial role in the production of vinegar. Most types of yeast can live only on sugars and starches. From these they produce carbon dioxide and alcohol. Yeasts reproduce by a method called budding. A small knob or bud forms on the parent cell, grows and finally separates to become a new yeast cell. Although this is the most common method of reproduction, yeasts also multiply by the formation of spores.

The yeast used in bread production consumes the sugars present in bread dough, using the energy for growth and reproduction and releasing carbon dioxide and alcohol. During this fermentation process, little bubbles of carbon dioxide released from the yeast fill the dough and cause it to expand or “rise.” A slice of bread can be examined with the naked eye or with a magnifying glass to see the many small spaces made by the carbon dioxide.

Some yeasts are psychrophilic, meaning they can grow at relatively low temperatures. In fact, the fermentation of wine and beer is often carried out at temperatures near 4°C (40°F). Some psychrophiles, can create a spoilage problem in meat coolers and other refrigerated storage areas.

Because yeasts can grow under conditions of high salt or sugar content, they can cause the spoilage of certain foods in which bacteria would not grow. Examples are honey, jellies, maple syrup, and sweetened condensed milk. Foods produced by the bacterial fermentation process, such as pickles and sauerkraut, can also be spoiled by yeasts which interfere with the desired bacterial process. Certain yeasts are pathogenic. However, yeast infections are much less common than are bacterial infections.

Mushrooms, toadstools, bracket fungi, shelf fungi, puffballs and other various parasites such as rust and smuts are called club fungi. Club fungi reproduce by spores. The mushroom is the fruiting body. The “roots” which are really the mycelium grow in very fertile soil or other plant and/or animal organic matter. The mycelium may live for years, slowly growing underground. Only when the conditions are favorable do mushrooms (the fruiting body) grow up above the surface. The spores are formed in the gills located within the “cap.” Under close examination the spores are produced in an area of the gills that are shaped like “clubs.”

Rusts are club fungi that produce rust-colored spores during one phase of their life cycle. Rusts are parasites on wheat, barley, oats, and other crops. Each year they cause millions of dollars of damage to crops. Smuts are similar to rusts. Their name refers to the black dusty-looking mass of spores they form within the tissues of the host plant. Smuts attack corn, wheat, oats, barley, and rye.

Interest Approach – Engagement

How are mushrooms different from plants? (don’t need sunlight, reproduce by spores, belong to kingdom Fungi)

If mushrooms don’t need light, where do they get their energy? (dead organic matter like compost or sawdust; other types of fungi also get energy from live organisms in symbiotic or parasitic relationships)

What conditions do mushrooms need to grow? (adequate moisture and temperature, organic matter for energy/nutrients)

Where do mushrooms grow naturally? (forest ecosystems)

How is a mushroom farm similar to a forest? How is it different? (the environmental conditions of the mushroom farm mimic a forest - moist and shaded with lots of decaying organic matter; on the farm people bring in organic matter to grow mushrooms on and the mushrooms are harvested when ready to eat; in the forest organic matter comes from dead trees and fallen leaves, some mushrooms are harvested by people and animals but many mature until they release spores and then their bodies decay)

What purpose do mushrooms serve on the farm? In the forest? (the main purpose of mushrooms on the farm is to provide food for people; in the forest mushrooms act as decomposers, breaking down organic matter and releasing nutrients into the soil, as well as a source of food)

Explain to students that, similar to the mushroom farm in the video, all farms can be thought of as ecosystems managed by people in order to grow populations of organisms (mushrooms, plants, animals) that are valuable to people for food, fiber, or other products. The following activities explore fungi related to food production and the ways in which they interact with living and nonliving components of the ecosystem.

Procedures

Activity 1: Spore Drop

Cut off mushroom stems just below the cap. Select an area where the spore print can be left undisturbed for 24 hours. Provide each individual or small group with a mushroom cap, sheet of paper or paper towel, and a cover.

Instruct students to place the mushroom cap, gill side down, on a white sheet of paper or paper towel.

Cover the mushroom cap with a dome and leave undisturbed for approximately 24 hours.

The next day, carefully remove the dome and mushroom cap.

Observe spores with a hand-lens. To preserve the spore pattern, spray it with hair spray or cover with clear, self-adhesive contact paper. Note: Do not spray the pattern if you plan to observe the spores under a microscope. Observe spores through a microscope, if desired. Discuss the spore pattern art. Are all patterns the same? Can you see each spore?

Share the How Mushrooms Grow image provided by the North American Mycological Association with students and discuss the life cycle of fungi. What environmental conditions do students think the mushroom spores would need to grow?

Activity 2: Grow Bread Mold

Show students the Moldy Bread Image, and tell them that the molds growing on the bread belong to the same kingdom as the mushrooms we grow to eat. The life cycle of a mold is just like the life cycle of a mushroom, but rather than a visible fruiting body, they grow tiny branches that form spores on the tip. Mold spores are so small they can’t be seen with the naked eye, except maybe as a puff of dust. Spores travel through the air, on animals, on human skin and clothes, and even get washed to new places by rain and streams. Mold spores are all around us, but they remain dormant until they land in a place that has the right conditions for growth.

Select four slices of bread, preferably from a loaf without preservatives (this will speed your mold growth). Give each piece the following treatment and then place the slice into a “treatment-labeled” Ziploc bag. Store the bags in warm dark place for incubation.

Wipe an unwashed hand (pretend you are smearing on mayonnaise with your entire hand) on both sides of the slice, place it into a Ziploc bag.

Lick one piece on both sides with your tongue.

Wipe one piece on both sides on the floor.

WASH YOUR HANDS. Place the slice onto a paper towel. Moisten the slice with water from a mister bottle.

Observe the bread for mold growth every other day for the next week. (This may take longer if you are using bread that contains preservatives.) Ask students to record their observations. At the end of two weeks review the results and make some class conclusions. Draw connections to ecology concepts: the slices of bread that touched the floor, your hand, and your tongue probably started with a higher population of spores; the slice moistened with water was in an environment with higher humidity.

Activity 3: Yeast Blowup

Tell students that mold is a fungus that causes bread to decompose, but another microorganism from the kingdom Fungi is used in making bread. Can they guess what it is? Yeast!

In one flask add cold tap water to the 100 ml mark (15°C, 60°F). In the second flask add warm water to the 100 ml mark (38°C, 100°F). In the third flask add boiling water to the 100 ml mark (100°C, 212°F). Swirl the flasks.

Place a balloon over each flask (three different colors help for identification).

Lead students through the following observations and discussion questions:

What do you observe in the first 5 minutes?

What do you observe in 20 minutes?

What do you observe in 60 minutes?

What is blowing up the balloons? (carbon dioxide from yeast respiration)

What was the best temperature? Why?

What do you think would happen if twice the sugar was added? How about half as much?

What do you think would happen if no sugar or flour were added?

Yeast is added to bread dough. Why does the bread rise? (carbon dioxide is trapped by the stretchy bread dough)

Will temperature affect how quickly bread will rise?

Can you see evidence of carbon dioxide bubbles in bread?

If you add more yeast to bread do you think it will rise faster?

How is yeast similar to mold? How is it different?

Activity 4: Reporting

After completion of the fungi observation activities, ask students to work in pairs. Randomly assign each pair a species of fungi from the list below. You may choose to print out the Species of Fungi for Research and Investigation list, cut apart the names, and have students draw their species out of a hat.

Agaricus bisporus

Alternaria solani

Amanita phalloides

Aspergillus fumigatus

Aspergillus terreus

Botrytis cinerea

Calvatia gigantea

Candida albicans

Cantharellus cibarius

Fusarium solani

Geotrichum candidum

Letinula edodes

Penicillium candidum

Pleurotus ostreatus

Rhyzoctonia solani

Saccharomyces cerevisiae

Trametes versicolor

Tuber melanosporum

Ask each pair of students to research their species and share their findings by creating a poster or other media that includes:

Common name

Life cycle/reproductive strategy (e.g., spores, budding)

Where species typically can be found

Interactions with living and nonliving components of ecosystems, including:

Feeding strategy (e.g., parasite, decomposer)

How the species affects or is used by people (Is this a desirable or undesirable species? Can it be both in different environments?)

How species is affected by temperature, humidity, light, etc.

How can growth of this species be promoted (if it's desirable) or limited (if it's undesirable)

Interactions with plants

Concept Elaboration and Evaluation

After conducting these activities, review and summarize the following key concepts:

Molds, yeasts, and mushrooms all belong to the kingdom Fungi.

Fungi can be both beneficial and harmful in farming and food production.

Changes to the physical and biological components of the ecosystem affect the growth of fungi.

Enriching Activities

Share some fun fungi math with your students. Did you know a mature mushroom can produce 2 billion spores in 4 days? How many hours does it take for a mushroom to produce 2 billion spores? (96 hours) How many spores can a mushroom produce in a day (24 hours)? (500 million) How long would it take to produce 1 billion spores? (2 days or 48 hours)

Try different variations for the Yeast Blowup activity: vary the amount of sugar, substitute whole wheat flour, use no flour, no sugar, add hot or cold water to the flask, test instant yeast versus standard yeast, etc.